Here's my second chapter. One note I want to make is the use of ゆうしん. edict has the entry 雄親 【ゆうしん】 (n) sire; male parent. However, the IME doesn't display that option for ゆうしん so I used hiragana. It can probly be picked up from context, but it's the vampire that turned Akami into a vampire. I don't really know of a good Japanese word for it. I probly had some other notes about this, but I'm slightly tired and can't remember anything else.

扉に近寄ったけど、- I think 近寄る means aproach to somebody(???) you have better use 扉に向いたけど

鉄夜は「なに」と言って赤美の顔に見た。ー 鉄夜は「なに」と言って赤美の顔を見た。

「帰りたくない。ここに残りたい。僕になる。」 - what do you mean?

「これ辞めて。迷惑だ。」 - やめる has ２ kanjis :止 and 辞. This last means "quit from the job", stop the job" (英語わからなくてすまんが、仕事に関係あるの言葉です！) So you have better use it in hiragana.

「何の意味？」 - どういう意味？

「どう？」 - どうすればいい？どうしたらいい？どうすれば手伝えるの？

「吸血鬼だね。夜が好きだろう？どう危ない？どう不便？」 - You can substitute どう by どこが？ どこが危ないか？ Doesn´t means "where is dangerous" but "what is dangerous?" as the phrase, あなたが挑戦から逃げて、どこが腰抜か？- you fled from the challenge, so who´s the coward here?

oh, I didn't realize that got turned into a kanji that I usually see used in a completely different way. It was too small to read. I should probly go with the hiragana しもべになる. Akami is basically telling him "You will be my servant"

しもべ is a common word in stories like these; it has an archaic or feudalistic flavor to it. 部下 has more of a mutual connotation to it than しもべ, which is more like a servant. I think that if you use the kanji 僕 for it, you should provide furigana because it's too easy to misread it as ぼく.